The present invention relates to an external cooling system for a molten film tube produced by a blown film tubular extrusion process, comprised of one or more enclosures with one or more respective cavities that directly receive a portion of cooling gas emanating from one or more associated cooling elements. Each enclosure includes a port containing a variable exhaust device and optional flow buffer, acting to maintain a pressure differential between the cavity and an adjacent inside volume of the molten film tube, adjustable to optimize molten film tube stability cooling element efficiency and spaced apart dimension between cooling elements. Significant increases in production speeds are achieved with improved film quality over an increased range of tubular film sizes, down to a minimum size which occurs when operating at zero internal to molten film tube pressure.

The invention provides a process to orient a high molecular weight polymer film, formed from molten, dispersed or dissolved state, characterised in that as a start of this orientation process the film becomes embossed in a pattern of closely spaced dots or thin short lines, 5 thereby becoming oriented within these embossments, whereafter the orientation process is continued in one or more steps by m.d. stretching, t.d. stretching, or combined m.d. and t.d. stretching, whereby the embossed and oriented dots or lines gradually grow and develop until essentially the entire film has become oriented.

The invention provides a process to orient a high molecular weight polymer film, formed from molten, dispersed or dissolved state, characterised in that as a start of this orientation process the film becomes embossed in a pattern of closely spaced dots or thin short lines, 5 thereby becoming oriented within these embossments, whereafter the orientation process is continued in one or more steps by m.d. stretching, t.d. stretching, or combined m.d. and t.d. stretching, whereby the embossed and oriented dots or lines gradually grow and develop until essentially the entire film has become oriented.

A cooling ring for cooling a film tube (14) in a film blowing installation, includes a cooling gas inlet (18), a distribution system (20) for distributing the cooling gas over the circumference of the film tube (14), a supply gap (28) for guiding the cooling gas in a radial direction towards the film tube, a cooling gas outlet forming an annular gap (34) that surrounds the film tube and is tilted at a tilt angle relative to the radial direction, a flexible adjusting ring (36; 36) arranged circumferentially in the annular gap, and a collar of individually controllable adjusting elements (44; 44) for local radial deformation of the adjusting ring, the adjusting ring arranged in engagement with a wall (32; 38) of the annular gap and forming a limiting wall (42) for the cooling gas flow exiting from the annular gap, the wall extending continuously in circumferential direction.

A cooling ring for cooling a film tube (14) in a film blowing installation, includes a cooling gas inlet (18), a distribution system (20) for distributing the cooling gas over the circumference of the film tube (14), a supply gap (28) for guiding the cooling gas in a radial direction towards the film tube, a cooling gas outlet forming an annular gap (34) that surrounds the film tube and is tilted at a tilt angle relative to the radial direction, a flexible adjusting ring (36; 36) arranged circumferentially in the annular gap, and a collar of individually controllable adjusting elements (44; 44) for local radial deformation of the adjusting ring, the adjusting ring arranged in engagement with a wall (32; 38) of the annular gap and forming a limiting wall (42) for the cooling gas flow exiting from the annular gap, the wall extending continuously in circumferential direction.

Aspects of the disclosure relate to manufacturing a balloon envelope for use in a stratospheric balloon system. For instance, a stream of polyethylene mixture is extruded through an extruder in order to orient molecules of polymer chains of polyethylene and to provide an oriented film. The oriented film is passed through an electron beam and thereby crosslinking the polymer chains to provide a cross-linked film. The cross-linked film is heat sealed to form the balloon envelope.

Aspects of the disclosure relate to manufacturing a balloon envelope for use in a stratospheric balloon system. For instance, a stream of polyethylene mixture is extruded through an extruder in order to orient molecules of polymer chains of polyethylene and to provide an oriented film. The oriented film is passed through an electron beam and thereby crosslinking the polymer chains to provide a cross-linked film. The cross-linked film is heat sealed to form the balloon envelope.

A film stretching unit uses a solar-thermal process temperature control system for a film stretching unit. The process temperature control system comprises at least a solar heat generator and a heat storage unit. A heat consumer circuit is connected to the heat storage unit in order to be capable of drawing stored thermal energy to supply a film stretching unit 1 with thermal energy.

A film stretching unit uses a solar-thermal process temperature control system for a film stretching unit. The process temperature control system comprises at least a solar heat generator and a heat storage unit. A heat consumer circuit is connected to the heat storage unit in order to be capable of drawing stored thermal energy to supply a film stretching unit 1 with thermal energy.

A method of forming a blown polymeric foam film is described herein. As described further below, equipment design (e.g., die design) and processing conditions may be controlled to form blown films having desired characteristics.